1. Field of the Invention
The present invention relates to a large caliber standard lens that may be used in single lens reflex (SLR) camera.
2. Description of the Related Art
Recently, cameras adopting an image sensor such as a charge coupled device (CCD) instead of using silver halide films have been widely used. Due to improvements in semiconductor integrating technology, high pixel count image sensors have been developed, and in response, lenses having excellent optical properties have been required. In addition, as demands of users for portable cameras increase, lenses having excellent optical properties and suitable for small sized cameras have been required.
Double Gauss type lenses or modifications thereof have been widely used as conventional bright standard lenses. Double Gauss type lenses have advantages in effectively compensating for spherical aberration by configuring symmetric optical systems with respect to an aperture diaphragm and increasing refractive power of a lens surface that faces the aperture diaphragm. However, double Gauss type lenses also have a disadvantage in occurring sagittal comatic flare.
To address the above disadvantage, configuration of a lens by restricting a radius of curvature of each lens and restricting refractive indexes and Abbe number of a lens material has been suggested. However, it is difficult to design a lens that may be fabricated easily while having excellent optical properties for high image quality.